1. Field of the Invention:
The present invention relates to an inexpensive and efficient energy-saving absorption refrigerating system and more particularly to an improvement for reducing the amount of operation energy which has heretofore been wasted in an absorption refrigerating system comprising an evaporator, an absorber, a generator or generators, a condenser, a heat exchanger or heat exchangers, piping interconnecting these and pumps.
2. Description of the Prior Art:
The amount of heat required to be provided by a heater for the operation of an absorption refrigerating system is generally shown by the following formula (1): EQU Q.sub.G .times.W.times..DELTA.i+LH.times.S (1)
where
Q.sub.G : Generator input heat PA1 W: Flow rate of a circulated solution PA1 .DELTA.i: Raise in enthalpy of the solution by heating PA1 LH: Latent heat of a refrigerant PA1 S: Amount of the refrigerant evaporated
The formula (1) can be divided into two portions, namely (A) portion comprising W.times..DELTA.i and (B) portion comprising LH.times.S. The (B) portion is proportional to refrigerating load and is effectively used as refrigerating output. The (A) portion, on the other hand, is radiated as a heat loss at a cooling tower provided in the cooling water circuit.
Regarding an absorption refrigerating system energy-saved operation is possible by keeping the flow rate of the circulated solution W at a desired level.
Examples of prior art are explained below based on attached figures.
FIG. 1 is a schematic illustration of a system representing one of the conventional single effect absorption refrigerating systems. FIG. 2 is a schematic illustration of a system representing one of the conventional double effect absorption refrigerating systems.
In the system illustrated in FIG. 1, there are provided an absorber 1, an evaporator 2, a generator 3, a condenser 4, a solution pump 5, a refrigerant pump 6, a heat exchanger 7, a steam pressure control valve 8, a level switch 9 and an overflow pipe 10.
In the system illustrated in FIG. 2, the components 1, 2, 4, 5, 6 and 8 represent the same as in FIG. 1. There are provided further a first generator 11, a second generator 12, a second heat exchanger 13, a first heat exchanger 14, a flow control valve 15, a drain heat exchanger 16 and drain trap 17.
The solution (absorbing liquid) in the absorber 1 which has been diluted by absorbing refrigerant used for chilling chilled water is fed by the solution pump 5 through the heat exchanger 7 to the generator 3, where the solution is concentrated separating refrigerant from the solution by means of the heat of steam or combustion gas. The separated refrigerant is condensed in the condensor 4 by the effect of cooling water. The concentrated solution returns through a heat exchanger to the absorber 1, where the solution is diluted by absorbing the refrigerant and is fed again to the generator 3 by means of the pump 5. The refrigerant condensed in the condenser 4 returns to the evaporator 2, where the refrigerant is used to chill the chilled water. The evaporator, absorber, generator or generators and condenser or condensers form a closed circuit and the total amount of the refrigerant and the solution in the system is always kept constant. In the cooling water circuit, a cooling tower (not shown in figures) is provided.
In this system, however, the (A) portion, W.times..DELTA.i, in the formula (1) is not proportional to refrigerating load and is constant since the flow rate W of the solution is constant by using a single fixed volume solution pump. Thus, under partial load condition, energy saving is not achieved since no change in the (A) portion causes the increase of Q.sub.G per unit refrigerating load.
In the double effect absorption refrigerating system, a flow control valve is provided in the solution line as shown 15 in FIG. 2 for energy saving under partial load condition. The use of a flow control valve allows linear flow rate control. However, due to valve characteristics, strict control is difficult. For example, 70% flow rate is obtained generally instead of 50% under 50% load. Therefore, the amount of saved energy is not satisfactory. In addition, expensiveness of the valve is another problem.
Further, there is a U.S. Pat. No. 3,279,206 relating to energy saving absorption refrigerating system which uses a variable capacity pump for energy saving operation under partial load condition by reducing the flow rate of a circulated solution W. However, it is a considerable problem that the use of a variable capacity pump is very expensive.
Therefore, it has been desired to achieve a reduction in operating cost and an increase in refrigerating system efficiency by decreasing W.times..DELTA.i of the (A) portion in the above mentioned formula (1) so as to reduce Q.sub.G as much as possible. In addition, it has been desired to achieve the same without using an expensive flow control valve or an expensive variable capacity pump.